The Connection Between Dry Weather In San Diego And The Polar Vortex
January 8, 2014 1:24 p.m.
Daniel Cayan, Ph.D. is a research meteorologist at the Scripps Institution of Oceanography and a researcher with the U.S. Geological Survey.
Eric Larson is executive director of the San Diego Farm Bureau.
CAVANAUGH: Our top story on Midday Edition, extreme winter weather has been dominating the national headlines for days. But it seems that here in San Diego, we've been living in it a land that winter weather forgot! So is there any connection between the below freezing temperatures in the east and our mild and very dry weather? When can we expect our winter rains to start? And what if anything does all this have to do with climate change? My guests, Dr. Daniel Cayan is a research meteorologist at Scripps institute of oceanographer. Welcome to the program.
CAYAN: Thank you.
CAVANAUGH: Eric Larson is executive director of the San Diego County farm bureau. Welcome back.
LARSON: Glad to be here.
CAVANAUGH: We've been hearing a lot about the polar vortex tenom that's caused extremely low temperatures back east. How unusual is this weather pattern?
CAYAN: Well, it's definitely unusual, and we're seeing a lot of extreme low temperatures back there at least for the last few decades. So this is a pattern that of course doesn't happen every year. But it's not unpress tented.
CAVANAUGH: How does it fit into the record?
CAYAN: It is one of the more extreme situations, but you can look back in the record and find episodes that you equally cold if not colder in many of the midwest and eastern states.
CAVANAUGH: Now, is there any connection between what we're experiencing here, a mild dry winter so far and the deep freeze going on back east?
CAYAN: Yeah, definitely. The atmosphere is a big fluid, and in correspondence with that deep low pressure system that's been inhabiting the eastern sector of the north American continent, we have had a very strong ridge here in the west and actually extending out into the north Pacific. It's all connected. With the weather in the east, you would expect the storm track is going to be --
CAVANAUGH: I'm sorry, is any of the weather in the west causing any of this low pressure that's happening?
CAYAN: Well, it's hard to say what's a chicken and what's an egg.
[ LAUGHTER ]
CAYAN: We can say that they go together. And when the pattern flattens out, storms will track across California and the warmer air will start flooding the eastern part of the country.
CAVANAUGH: What exactly is causing the dry mild weather here?
CAYAN: Well, this high pressure ridge this is not the ultimate cause. But the sort of immediate situation is that we have this very strong high pressure dome that's been operating over the eastern north Pacific and the west coast. And in fact, in the last several weeks, the whole west coast, not only Southern California, but virtually all the way into the southern part of British Columbia has been drier than normal. So it's been like a big shield that's been warding off the storms. And as you finally get up into coastal Alaska and British Columbia, you see active precipitation. But everything south of there has been extremely dry.
CAVANAUGH: And it's sort of forcing everything up so that when it comes down in the middle of the country, it's coming down from some very, very cold areas.
CAYAN: Yeah, we're getting that really refrigerated, fairly dry air. It hasn't been extremely wet in the plains in the east. But they certainly have been getting this cold air deployed along with this system.
CAYAN: Eric Larson, how closely are local farmers watching for our usual winter rainfall to start kicking in
LARSON: They're watching every day, and looking at their long-term weather reports saying when is that rain going to come? Rain is incredibly important to our farmers, especially the tree crop growers. Any rain we don't get, they're going to have to buy water to replace the rain we don't receive. So they want to know if there's a chance that rain is coming so they can maybe put off an irrigate cycle or two in anticipation of the rain. So far it's just been disappointment after disappointment, and the water bills are creeping up and creeping up.
CAVANAUGH: This is shaping up to be the 3rd year of drought in all of California. How have we been doing here in San Diego County?
LARSON: Well, a lot of credit needs to be given to the county Water Authority for having a really diverse portfolio of water sources and working with the Metropolitan Water District, having a lot of storage on hand. So as San Diegans, we're not feeling this pinch just yet. They're talking about getting to 2014, we need to worry about 2015. We've got cities in Northern California that are talking about going on emergency rations for water right now. The governor is considering a drought declaration for the State of California. The farmers are really concerned that there could be mandatory cutbacks on water in 2015.
CAVANAUGH: Not this year though?
LARSON: Not this year.
CAVANAUGH: Dan, even though California's weather is volatile, is there any indication that what we're seeing now is connected to global climate change?
CAYAN: Well, that's a hard question. It's very hard to attribute individual events to long-term trends. And even though in the long-term, we're seeing some unease signs in the climate models toward drying in Southern California, I would say the major reason for this particular episode is just the natural variability of the climate system. Southern California is just notoriously variable in a relative way concerning our precipitation of anywhere in the conterminous United States. So we are seeing that big-time in this last episode you mentioned that we're now entering the third year of dryness.
CAVANAUGH: And some say the length of time the weather events continue though may be connected to climate change. Do you agree with that?
CAYAN: Yeah, that's one of the signatures. But again, I'm not sure that this one really stands out amongst others. You can point to historical dryness in California and find multi-year dry episodes. We had the spade of dryness in the late '80s and early '90s. Five or six years in a row of subpar precipitation. Our area is just prone to this. And the winter is not over. We literally have -- essentially half of the windows still open as far as the seasonal opportunity for north Pacific storms. So there's a possibility that we could get ourselves out of at least part of this deficit.
CAVANAUGH: Dan, tell us more about that window of opportunity we have for rain in San Diego. It extends through march?
CAYAN: Basically our climate is one where the storm systems start to activate in the fall immediate or late fall. November, and then essentially there's chances of pretty good precipitation that goes through the month of March. And sometimes on onto April. But if this continues for another month or so, we've really lost the core of the winter season. And that's why Eric and his clientel are nervous about this situation.
CAVANAUGH: We woke up this morning. It was cloudy. It looked like it might rain. I saw a weather forecast the end of last week that said it would rain tomorrow. But that's not really in the forecast anymore. Do we see any rain on the horizon?
CAYAN: I don't think there's anything that is really remarkable in the next week or so. The forecasts that you're referring to are skillful out to somewhere in the one-week timeframe. And beyond there, it's -- the atmosphere is kind of resetting itself, it's very volatile and so forth. So we'll just have to wait and see. But there's a chance that somewhere along the line this winter, we're going to see the westerlies reappear, and the cyclones move across.
CAVANAUGH: Good chance?
CAYAN: Well, I think there's a fair chance. But I think there's a -- it's going to be difficult to recover to a normal winter. To have a whole winter that was as barren as the one we've seen so far.
CAVANAUGH: Back to what you've been saying about growers across the state pressuring the governor to call for a drought emergency even now before we know for certain how wet this winter is going to be, what would a proclamation like that do for agriculture?
LARSON: It's not just what it does for agriculture. And those people calling for it are more than the farmers. A lot of the water we don't receive is because it comes through a place like the Sacramento dementia that's protected by a lot of environmental law. If there's a drought declaration, the governor may have some capacity to set aside some of those regulations and start to weigh the value of leaving the water in a place like the delta and importing more of it south. It just might give them access to some larger amount of water at the expense of some other use.
CAVANAUGH: San Diego County because of its various access to various sources of water now. Is in better than a lot of other places in Southern California. Are we in an unusual situation here with Southern California actually look at having more water in the coming months than Northern California?
LARSON: It's very unusual that the cities and the communities that are in dire straits right now are in the northern part of the state. They actually live off the rainfall or the aqueducts that pass the water N. Southern California, we've always recognized because of these fluctuations, we have to bank water and store it. With these long dry period, the amount of water we can store doesn't get us all the way through. We have a lack of storage for the entire state.
CAVANAUGH: How are San Diego County farmers preparing for another potential drought season?
LARSON: What's happening, a lot of farmers are actually deciding to quit irrigating their crops. And the crop on the edge of that right now are avocados. They're very expensive to irrigate. They grow wonderfully here. It's the best avocados grown in the world, but they're expensive to irrigate. So unfortunately, we've seen a doubling of the price of water since 2006. And we've lost about 10,000 acres of avocados in that period of time as growers just can't compete in the marketplace. If we don't get the rain and don't get a chance to set aside some of the water purchases that the farmers have to make, ultimately, we'll see additional farmers decide to turn their water off on their farms. If it goes to the extreme, and weep get to a year let's say 2015, if we end up with a 3rd, 4th year of dryness, farmers could be facing mandatory cuts. And the way the system is set up, farmers will get cut first before the residents and the commercial and industrial users are asked to cut their water use. That's a concern for the farmers all the time.
CAVANAUGH: How well do you think state and local leaders are responding to the current drought and perhaps even more broadly, the specter of climate change?
LARSON: Well, I think everybody is paying close attention now. Our problem is that since about 1982 till now, we really haven't paid attention to the infrastructure of the water system in California. Our system was completed with 17 million people in the state, now there's 37 million. We not only have to fix those problem, we have to go back and fix a lot of problems we didn't take care of. So we have an awful lot of infrastructure issues we have to take care of, most important uponly the dealt A. The -- importantly, the delta. It has a lot of problems structurally. And we don't have a lot of places we can store the water in a wet year.
CAVANAUGH: And Daniel?
CAYAN: Ditto. He did a good job of laying that out. I would say that conveyance, the ability to move water is another issue, and of course the possible designing of a route around the delta is in in proposition right now and being worked on. As far as the state taking the long view, I think California actually shines in the midst of other states in the U.S. in its forward thinking. We have had three administrations now, two by Schwarzenegger, and now governor brown that have actually been planning about climate change and making plans. So I'm encouraged by what I see in California. There's a lot of work to do. But I think that's a lot of minds working on this.